1. Field of the Invention
The present invention relates to a driving method of a PDP(Plasma Display Panel), and more particularly, to a driving method of a PDP capable of preventing abnormal discharge and dielectric breakdown due to excess charged particles collected on the outside of a display screen.
2. Background of the Related Art
FIG. 1 illustrates a schematic view of a conventional surface-discharge type AC PDP(Plasma Display Panel). The surface-discharge AC PDP includes a front glass substrate 1, an address electrode 3 formed on the front glass substrate 1, a rear glass substrate 2 opposed to the front glass substrate 1, electrodes X and Y (7 and 8) arranged parallel to each other on the rear glass substrate 2, a dielectric layer 6 formed to cover the electrodes X and Y, an MgO protection layer formed on the dielectric layer, and a barrier 4 disposed between the front glass substrate 1 and the rear glass substrate 2 and dividing a discharge space.
FIG. 2 illustrates an arrangement of driving electrodes of the PDP of FIG. 1. The driving electrodes include a plurality of address electrodes A1, A2, A3, . . . , Am−1 and Am arranged parallel to one another and a plurality of electrodes X and electrodes Y Y1, Y2, Y3, . . . , Yn−1 and Yn arranged approximately vertical to the address electrodes. Discharge cells are formed at intersections of the electrodes X and Y and the address electrodes, electrodes Y are scan electrodes and electrodes X are common electrodes connected commonly.
FIG. 3 illustrates an ADS(Address Display-period Separation) method for driving the PDP of FIGS. 1 and 2. In the ADS method, 1 field of video signal is divided into 8 sub-fields; each sub-field consisting of a reset period, an address period and a sustain period. The reset period is a period for initializing the discharge cells by discharging all discharge cells of FIG. 2, the address period is a period for designating the discharge cells to be displayed according to video signal input, and the sustain period is a period for sustain discharge to the discharge cells designated in the address period. In the sustain period of each sub-field, a weight value is assigned as a display period, thereby combining the sub-fields to display multi-grade.
In general, scan lines Y1, Y2, Y3, . . . , Yn−1 and Yn of the PDP of FIG. 2, in case of a VGA(Video Graphics Array), consist of 480 lines, and the address operation is carried out by scanning to each line in a line sequential method, and at the same time, applying data signal through the address electrodes. As shown in FIG. 3, in the ADS method of dividing 1 video field into 8 sub-fields and having the address periods for all scan lines every sub-field, the scan period of 1 scan line is about 2.5 μs, and a period for scanning the whole 1 video field is approximately 2.5 (μs)×480 (lines)×8 (sub-fields), namely 9.6 μs. Because it takes 9.6 μs to scan if the 1 video field is about 16.7 μs, the residual period, that is, 7.1 μs is used for gray scale. However, if the number of the sub-fields is increased to 10 to remove false contour or to increase the number of gray scales, the scan period is 2.5 (μs)×480 (lines)×10 (sub-fields), namely 12 μs, and so, display must be performed in very high frequency because there is the period for the gray scale of only 4.7 μs left. Furthermore, In case that scan lines over 760 are used in an HD TV(High Definition TV), the scan period is 2.5 (μs)×760 (lines)×8 (sub-fields), namely 15.2 μs; most of 1 video period being used for the scan period.
To solve the above problems, as shown in FIG. 4, there is used a driving method of dividing the address electrodes into upper and lower parts. The method has a disadvantage that a plurality of driving ICs are used, but has several advantages that sub-fields more than that of the prior arts can be applied and the method can be used in the HD TV of scan lines over 760 by reducing the scan period to ½.
FIG. 5 illustrates a scan sequence in a driving method of a conventional PDP. In the scan sequence, a scan pulse is applied to the scan electrodes (electrodes Y) of 1, 2, . . . and 480 lines every sub-field in order, and at the same time, an input video data pulse is applied to the address electrodes. At this time, if the scanning is performed repeatedly, electric potential rises or falls by accumulation or vanishment of excess charged particles on the outer portion of a display screen adjacent to the scan electrode of the final line, i.e., the 480th line. So, there occurs abnormal discharge on the cells in vicinity of the scan electrode of the 480th line, thereby reducing reliability by deteriorating video quality or by occurring dielectric breakdown.
In the same way, FIG. 6 illustrates a scan sequence in a driving method of a conventional PDP in which address electrodes are divided into two. For example, when an addressing is performed in order of 1st˜240th lines and in order of 241st˜480th, electric charges are abnormally collected on a boundary between upper address electrodes and lower address electrodes, i.e., a central part, and on the outer portion of a display screen of 480th line and electric potential rises, thereby, occurring abnormal discharge on the cells in vicinity of the central part and of the 480th line to deteriorate the video quality or generate dielectric breakdown.